150+ Scientific Studies Showing the Dangers of Marijuana


This story comes from POPULAR TECHNOLOGY.net, reprinted with permission from the author.

Perception of marijuana as a “safe drug” is scientifically inaccurate (University of Montreal)
Cannabis more damaging to health than previously thought claim doctors (Imperial College London)


Brain Damage:

Adolescent Pot Use Leaves Lasting Mental Deficits (Duke University)

Brain-damage risks higher for younger marijuana users, study says (Harvard Medical School)

Cannabis and adolescence: A dangerous cocktail (McGill University Health Centre)

Cannabis ‘can cause psychosis in healthy people’ (King’s College London)

Cannabis Could Increase Risks Of Psychotic Illness By 40 Percent (Cardiff University)

Cannabis increases risk of psychosis (British Medical Journal)

Cannabis increases risk of depression and schizophrenia (British Medical Journal)

Cannabis ingredient causes toxic psychosis (University of Lausanne)

Cannabis link to psychosis (University of New South Wales)

Cannabis smokers ‘are taking huge risk of psychotic illness’ (King’s College London)

Cannabis smoking ‘permanently lowers IQ’ (Proceedings of the National Academy of Sciences)

Cannabis Triggers Transient Schizophrenia-like Symptoms (Yale School of Medicine)

Cannabis use ‘dulls the brain’ (Journal of the American Medical Association)

Cannabis use mimics cognitive weakness that can lead to schizophrenia (University of Bergen)

Cannabis use precedes the onset of psychotic symptoms in young people (British Medical Journal)

Casual marijuana use linked to brain abnormalities in students (Northwestern University)

Chronic alcohol and marijuana use during youth can compromise white-matter integrity (University of Pittsburgh Medical Center)

Concerns over mental health risk of smoking cannabis (British Journal of Psychiatry)

Daily Consumption Of Cannabis Predisposes To Appearance Of Psychosis And Schizophrenia (University of Granada)

Daily Pot Smoking May Hasten Onset of Psychosis (Emory University)

Early Cannabis Use Increases Risk of Schizophrenia (University of Otago)

Early cannabis users three times more likely to have psychotic symptoms (University of Queensland)

Frequent Marijuana Use May Affect Brain Function (University of Iowa)

Heavy Cannabis Use May Lead to Psychotic Symptoms (University of Otago)

Heavy Marijuana use has a detrimental impact on intelligence (Canadian Medical Association Journal)

Heavy Marijuana Use May Damage Developing Brain In Teens, Young Adults (Children’s Hospital of Philadelphia)

How cannabis causes ‘cognitive chaos’ in the brain (University of Bristol)

How Marijuana Causes Memory Deficits (Nature Neuroscience)

How marijuana impairs memory (Cell Journal)

How Smoking Marijuana Damages The Fetal Brain (Science)

Human Study Shows Greater Cognitive Deficits in Marijuana Users Who Start Young (Society for Neuroscience)

Imaging Shows Similarities in Brains of Marijuana Smokers, Schizophrenics (Radiological Society of North America)

Imaging Study Shows Awareness Deficit in Marijuana Abusers (Neuropsychopharmacology Journal)

Lab study shows THC exposure as adolescents linked to negative effects of THC as adults (Federation of American Societies for Experimental Biology)

Long-time cannabis use associated with psychosis (Archives of General Psychiatry Journal)

Long-term cannabis use causes brain injury (Archives of General Psychiatry Journal)

Long-term cannabis use may blunt the brain’s motivation system (Imperial College London)

Marijuana And Alcohol Taken Together Induced Widespread Nerve Cell Death In Brains Of Young Rats (Annals of Neurology Journal)

Marijuana has damaging effect on brain (King’s College London)

Marijuana Use Affects Blood Flow In Brain Even After Abstinence (American Academy of Neurology)

Marijuana use in adolescence may cause permanent brain abnormalities (University of Maryland Medical Center)

Marijuana use in pregnancy damages kids’ learning (Proceedings of the National Academy of Sciences)

Marijuana Users Have Abnormal Brain Structure and Poor Memory (Northwestern University)

Memory, speed of thinking get worse over time with marijuana use (American Academy of Neurology)

Mental illness associated with heavy cannabis use (Centre for Addiction and Mental Health)

Molecular Imaging Shows Chronic Marijuana Smoking Affects Brain Chemistry (Society of Nuclear Medicine)

More Evidence Links Early Cannabis Use to Psychosis (City University of New York)

More evidence of cannabis-induced psychosis (BMC Psychiatry Journal)

New RCSI research demonstrates how cannabis use during adolescence affects brain regions associated with schizophrenia (Royal College of Surgeons in Ireland)

New research reveals how cannabis alters brain function (King’s College London)

Psychotic illness appears to begin at younger age among those who use cannabis (Archives of General Psychiatry Journal)

Rat study conducted by UGA researchers suggests that cannabis interferes with sustained attention (University of Georgia)

Research Finds that Marijuana Use Takes Toll on Adolescent Brain Function (University of Cincinnati)

Scans reveal brain damage from cannabis is like schizophrenia (Albert Einstein College of Medicine)

Schizophrenia Linked To Dysfunction In Molecular Brain Pathway Activated By Marijuana (University of Pittsburgh School of Medicine)

Skunk ‘poses greatest risk of psychosis’ (King’s College London)

Skunk smokers 18 times more likely to be psychotic (Royal College of Psychiatrists)

Smoking cannabis increases the risk of depression in the case of genetic vulnerability (Radboud University)

Starting marijuana use during teens may result in cognitive impairment later in life (National Institute on Drug Abuse)

Study demonstrates link between reclassification of cannabis and cannabis psychosis (University of York)

Study Links Marijuana to Brain Problems (Journal of the American Medical Association)

Teen Drug Use Associated With Psychiatric Disorders Later In Life (National Institute On Drug Abuse)

Teen Marijuana Use Can Lead to Anxiety, Depression, or Aggression (Mount Sinai School of Medicine)

Teen Marijuana Use Worsens Depression: An Analysis of Recent Data Shows ‘Self-Medicating’ Could Actually Make Things Worse (Office of National Drug Control Policy)



Cannabis alters human DNA — new study (University of Leicester)

Higher Cancer Risk Found in Marijuana Than in Tobacco (Indiana University)

Marijuana Use Linked to Increased Risk of Testicular Cancer (Fred Hutchinson Cancer Research Center)

Marijuana use may increase risk of testicular cancer (University of Southern California)

New study reveals how cannabis suppresses immune functions: Cannabis compounds found to trigger unique immune cells which promote cancer growth (European Journal of Immunology)

Researchers At UCLA’s Jonsson Cancer Center Report Smoking Marijuana May Increase Risk Of Head And Neck Cancers (University of California, Los Angeles)

Sexual Activity and Marijuana Use Associated with HPV-Positive Head and Neck Cancer, Study Shows (Johns Hopkins Kimmel Cancer Center)

Study finds marijuana ingredient promotes tumor growth, impairs anti-tumor defenses (National Institute on Drug Abuse)

Tobacco is ‘less risky than dope’ (Memorial Sloan–Kettering Cancer Center)



German study finds cannabis use triggered 2 deaths (Forensic Science International Journal)


Gum Disease:

Heavy Marijuana Use Linked To Gum Disease (Journal of the American Medical Association)


Heart Disease:

Adolescent binging on marijuana linked to stroke (Saint Louis University)

Marijuana use can trigger heart attack (Beth Israel Deaconess Medical Center)

Marijuana use may increase heart complications in young, middle-aged adults (American Heart Association)

Regular Cannabis May Increase Risk Of Stroke In Young Users (British Medical Journal)

Smoking Marijuana Associated With Higher Stroke Risk in Young Adults (American Heart Association)

Study Finds Marijuana Poses Health Threat to Baby Boomers (Beth Israel Deaconess Medical Center)

Study finds possible connection between marijuana abuse and stroke or heart attacks (Molecular Psychiatry Journal)


Lung Disease:

Growing Evidence Of Marijuana Smoke’s Potential Dangers (American Chemical Society)

Impact on lungs of 1 cannabis joint equal to up to 5 cigarettes (British Medical Journal)

Long-term Marijuana Smoking Leads To Respiratory Complaints (Yale School of Medicine)

Marijuana associated with same respiratory symptoms as tobacco (Yale School of Medicine)

Marijuana Smoke Contains Higher Levels Of Certain Toxins Than Tobacco Smoke (American Chemical Society)

Marijuana Smokers Face Rapid Lung Destruction — As Much As 20 Years Ahead Of Tobacco Smokers (Respirology Journal)

Marijuana Smoking Increases Risk Of COPD For Tobacco Smokers (Canadian Medical Association Journal)

Marijuana Worsens COPD Symptoms In Current Cigarette Smokers (American Thoracic Society)

Research Confirms Adverse Effects of Cannabis on Respiratory Health (University of Otago)

Smoking One Joint is Equivalent to 20 Cigarettes (Medical Research Institute of New Zealand)



Binge eating, overeating may be associated with initiating use of marijuana, other drugs (Archives of Pediatrics & Adolescent Medicine Journal)

Machinery Of The ‘Marijuana Munchies’ (Neuron Journal)



Cannabis use linked to risk of osteoporosis (Nature Medicine)


Pregnancy Complication:

Cannabis during pregnancy endangers fetal brain development (Karolinska Institutet)

Marijuana Use Causes Early Pregnancy Failure (Journal of Clinical Investigation)

Marijuana use could cause tubal pregnancies (Vanderbilt University Medical Center)

Marijuana Use Implicated in Pregnancy Problems (Cincinnati Children’s Hospital Medical Center)

Substance use, social stress compromise pregnant women’s immune system (Duke University Medical Center)


Sexual Dysfunction:

Abusing Marijuana May Overload System, Inhibit Fertility (University at Buffalo)

Marijuana-Like Compounds May Alter Human Fertility (University at Buffalo)

Researcher connects cannabis use and sexual dysfunction (Queen’s University)

Sperm From Marijuana Smokers Move Too Fast Too Early, Impairing Fertility (University at Buffalo)


Sleep Disorder:

Marijuana use is associated with impaired sleep quality (American Academy of Sleep Medicine)


Viral Infection:

Marijuana Component Opens The Door For Virus That Causes Kaposi’s Sarcoma (American Association for Cancer Research)

Regular Marijuana Use Increases Risk Of Hepatitis C-related Liver Damage (American Gastroenterological Association)


Vehicle Accidents:

Cannabis almost doubles risk of fatal crashes (British Medical Journal)

Cannabis use doubles chances of vehicle crash (British Medical Journal)

Driving under influence of cannabis more common and riskier than drink driving (University of Otago)

Marijuana use involved in more fatal accidents in Colorado (University of Colorado School of Medicine)

Marijuana use may double the risk of accidents for drivers (Columbia University)

Signs point to sharp rise in drugged driving fatalities (Columbia University)

Study finds cannabis use, dangerous driving behaviors interrelated (University of Montreal)

Teens who use alcohol and marijuana together are at higher risk for unsafe driving (Journal of Studies on Alcohol and Drugs)

The dangers of taking the “high” road: Increased collision risk, skill impairment (Dalhousie University)



Animals Exposed To Marijuana’s Active Component Will Self-Administer The Drug (National Institute on Drug Abuse)

Cannabis withdrawal symptoms might have clinical importance (Public Library of Science Journal)

Chronic Marijuana Users Become Aggressive During Withdrawal (Harvard Medical School)

Increase in prevalence of marijuana abuse and dependence (Journal of the American Medical Association)

Marijuana Withdrawal As Bad As Withdrawal From Cigarettes (Johns Hopkins University School of Medicine)

Marijuana Withdrawal Reported By Teens Seeking Treatment (University of Vermont)

Mothers’ Teen Cannabinoid Exposure May Increase Response of Offspring to Opiate Drugs (Tufts University)

Parental exposure to THC Linked to drug addiction, compulsive behavior in unexposed offspring (Mount Sinai Medical Center)

Regular cocaine and cannabis use may trigger addictive behaviours (British Journal of Pharmacology)

Smoking, Drinking, Drugs: The Younger They Start, The Harder It Is To Quit (Center for Advancing Health)

Troubled Teens Risk Rapid Dependence on Marijuana (University of Colorado School of Medicine)


Gateway Drug:

A ‘yes’ to one drug could become ‘yes’ for other drugs (Prevention Science Journal)

Cannabis linked to use of amphetamines (Addiction Journal)

Brain Studies Tie Marijuana to Other Drugs (Science)

Early marijuana use increases risk of drug and alcohol problems later in life (Washington University School of Medicine)

Illicit Drug Use Starts With Cannabis (University of Otago)

Marijuana use linked to hallucinogen use (Johns Hopkins University Bloomberg School of Public Health)

National Study Shows “Gateway” Drugs Lead to Cocaine Use (Columbia University)

Study suggests cannabis-users may be vulnerable to harder drugs (Mount Sinai School of Medicine)



Decriminalizing pot may land more kids in the ER (American College of Emergency Physicians)

High School Seniors’ Marijuana Use Expected to Increase with Legalization (New York University)

Increase in unintentional marijuana ingestion among children following new drug laws in Colorado (Journal of the American Medical Association Pediatrics)

Legalizing marijuana in California would lower the price of the drug and increase use (RAND Corporation)

Legalizing marijuana in California would not substantially cut cartel revenues (RAND Corporation)



African-American Girls Who Use Marijuana Engage In Riskier Sex, Have Higher STD Rate (Emory University)

Children who smoke cannabis are twice as likely to offend (Queen’s University Belfast)

Early Exposure To Drugs, Alcohol Creates Lifetime Of Health Risk (Psychological Science Journal)

Father’s incarceration associated with elevated risks of marijuana and other illegal drug use (Bowling Green State University)

First-Year College Students Show High Rate of Cannabis Use Disorders (University of Maryland, College Park)

Future generations could inherit drug and alcohol use (Sam Houston State University)

Malt Liquor Linked To Marijuana Use Among Young Adults (University at Buffalo)

New study finds glamorization of drugs in rap music jumped dramatically over two decades (University of California, Berkeley)

One Of Every Three Popular Songs Contains References To Substance Use (American Public Health Association)

Pot and pop: New research finds stronger link between music and marijuana use among teens (University of Pittsburgh Schools of the Health Sciences)

References To Explicit Substance Use Common In Popular Music (Archives of Pediatrics & Adolescent Medicine Journal)

Researchers Find Factors That Encourage Cannabis Use Among University Students (Journal of Applied Biobehavioral Research)

Rising Teen Marijuana Use Is Fueled By Change In Attitudes (American Journal of Public Health)

Teens who frequently go out with friends more likely to use marijuana (Archives of Pediatrics & Adolescent Medicine Journal)

Medical Marijuana Myth – Alzheimer Treatment:

Marijuana ineffective as an Alzheimer’s treatment (University of British Columbia)


Medical Marijuana Myth – Multiple Sclerosis (MS) Treatment:

Active ingredient of cannabis has no effect on the progression of multiple sclerosis (Peninsula College of Medicine and Dentistry)

Added benefit of Cannabis sativa for spasticity due to multiple sclerosis is not proven (Institute for Quality and Efficiency in Health Care)

Cannabis constituent has no effect on MS progression (Plymouth University)

Jury’s Still Out on Use of Marijuana Derivative for MS (American Academy of Neurology)

Marijuana Use May Hurt Intellectual Skills in MS Patients (American Academy of Neurology)

No strong evidence to back use of cannabis extract in Multiple Sclerosis (British Medical Journal)

Smoking Marijuana Impairs Cognitive Function in MS Patients (American Academy of Neurology)


Medical Marijuana Myth – Nausea Relief:

Marijuana use associated with cyclic vomiting syndrome in young males (Neurogastroenterology and Motility Journal)

Marijuana use may cause severe cyclic nausea, vomiting, a little-known, but costly effect (American College of Gastroenterology)

Severe Vomiting Sickness With Chronic Cannabis Abuse (World Journal of Gastroenterology)


Medical Marijuana Myth – Pain Relief:

Active ingredients in marijuana found to spread and prolong pain (University of Texas Medical Branch at Galveston)

Cannabis ‘no better than codeine’ for headaches (British Medical Journal)

Doubts on cannabis for pain relief (Flinders Medical Centre)

Endocannabinoids can promote pain (ETH Zurich)

Medical Marijuana Not the Answer for Teens with Chronic Pain, Mayo Clinic Doctors Say (Mayo Clinic)

Oral Cannabis Ineffective In Treating Acute Pain (Journal of Anesthesiology)

Too Much Marijuana Makes Pain Worse, Not Better (University of California, San Diego)


Sources: (124)

Addiction Journal

Albert Einstein College of Medicine

American Academy of Neurology

American Academy of Sleep Medicine

American Association for Cancer Research

American Chemical Society

American College of Emergency Physicians

American College of Gastroenterology

American Gastroenterological Association

American Heart Association

American Journal of Public Health

American Public Health Association

American Thoracic Society

Annals of Neurology Journal

Archives of General Psychiatry Journal

Archives of Pediatrics & Adolescent Medicine Journal

Autonomous University of Barcelona

Beth Israel Deaconess Medical Center

BMC Psychiatry Journal

Bowling Green State University

British Journal of Pharmacology

British Journal of Psychiatry

British Medical Journal

Canadian Medical Association Journal

Cardiff University

Cell Journal

Center for Advancing Health

Centre for Addiction and Mental Health

Children’s Hospital of Philadelphia

Cincinnati Children’s Hospital Medical Center

City University of New York

Columbia University

Dalhousie University

Duke University

Duke University Medical Center

Emory University

ETH Zurich

European Journal of Immunology

Federation of American Societies for Experimental Biology

Flinders Medical Centre

Forensic Science International Journal

Fred Hutchinson Cancer Research Center

Harvard Medical School

Imperial College London

Indiana University

Institute for Quality and Efficiency in Health Care

Johns Hopkins Kimmel Cancer Center

Johns Hopkins University Bloomberg School of Public Health

Johns Hopkins University School of Medicine

Journal of Anesthesiology

Journal of Applied Biobehavioral Research

Journal of Clinical Investigation

Journal of Studies on Alcohol and Drugs

Journal of the American Medical Association

Journal of the American Medical Association Pediatrics

Karolinska Institutet

King’s College London

Mayo Clinic

McGill University Health Centre

Medical Research Institute of New Zealand

Memorial Sloan–Kettering Cancer Center

Molecular Psychiatry Journal

Mount Sinai Medical Center

Mount Sinai School of Medicine

National Institute on Drug Abuse

Nature Medicine

Nature Neuroscience

Neurogastroenterology and Motility Journal

Neuron Journal

Neuropsychopharmacology Journal

New York University

Northwestern University

Office of National Drug Control Policy

Peninsula College of Medicine and Dentistry

Plymouth University

Prevention Science Journal

Proceedings of the National Academy of Sciences

Psychological Science Journal

Public Library of Science Journal

Queen’s University

Queen’s University Belfast

Radboud University

Radiological Society of North America

RAND Corporation

Respirology Journal

Royal College of Psychiatrists

Royal College of Surgeons in Ireland

Saint Louis University

Sam Houston State University


Society for Neuroscience

Society of Nuclear Medicine

Tufts University

University at Buffalo

University of Bergen

University of Bristol

University of British Columbia

University of California, Berkeley

University of California, Los Angeles

University of California, San Diego

University of Cincinnati

University of Colorado School of Medicine

University of Granada

University of Georgia

University of Iowa

University of Lausanne

University of Leicester

University of Maryland, College Park

University of Maryland Medical Center

University of Montreal

University of New South Wales

University of Otago

University of Pittsburgh Medical Center

University of Pittsburgh School of Medicine

University of Pittsburgh Schools of the Health Sciences

University of Queensland

University of Southern California

University of Texas Medical Branch at Galveston

University of Vermont

University of York

Vanderbilt University Medical Center

Washington University School of Medicine

World Journal of Gastroenterology

Yale School of Medicine

Marijuana can cause – Brain Damage (Lowered IQ, Memory Loss, Paranoia, Psychosis, Schizophrenia); Mood Disorders (Aggression, Anxiety, Depression, Irritability); Cancer; Heart Attacks; Gum Disease; Impaired Motor Skills; Lung Disease; Obesity; Osteoporosis; Pregnancy Complications; Sexual Dysfunction; Strokes, Viral Infections and even Death.

If you are a parent looking for help with a child please contact:

Partnership for Drug-Free Kids

1-855-DRUGFREE (1-855-378-4373) Monday-Friday 10am-6pm ET



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